Existing tissue sample treatment methods, in some applications, comprise a number of steps that are performed manually. For example, in immunologic applications, such as in-situ hybridization (ISH) and immunohistochemical (IHC) applications, some steps including dewaxing and target retrieval are performed manually by an operator to treat the tissue sample before it can be used in a staining apparatus for staining the tissue sample according to a predetermined staining protocol. In this example, tissue samples are preserved in formalin and presented on microscope slides with a layer of paraffin wax protecting the sample. Thus, treatment in the form of at least dewaxing by heat and/or use of reagent is required to be performed by the operator on the slide before treatment in the form of staining of a sample can take place. Dewaxing is typically achieved by the operator manually dunking the slide in a dewaxing solution (e.g. a dewaxing reagent) to prepare the sample for staining. Also, the sample may be further treated by manually immersing the slide in another reagent, such as alcohol, to dehydrate the sample before staining can take place. In any event, the dewaxed sample on the slide is typically loaded into the staining apparatus by the operator for staining and is later retrieved by the operator after the staining process has been completed for viewing by, say, a pathologist.
Attempts have been made to automatically treat tissue samples disposed on slides for immunologic applications using, for example, an automated tissue sample staining apparatus. In this example, the automated staining apparatuses treat tissue samples using reagents to treat the sample before staining the samples on the slides. The treatment of the samples is also typically performed automatically by one or more robots configured to dispense reagents to the samples on the slides in a predetermined sequence according to a staining protocol. In addition, the robots can also be configured to dispense reagents such as dewaxing solution and alcohol to treat the samples on slides before and after staining. The reagent currently being dispended by one of the robots, however, must be purged from the robots before other reagents can be dispensed causing delay, reagent wastage and inefficient use of the automated staining apparatus.